Allocating Bandwidth to Queue
The Dell Networking recommends pre-calculating your bandwidth requirements before creating them.
Make sure you apply the QoS policy to all the four queues and that the sum of the bandwidths allocated
through them is exactly 100.
When you apply the QoS policies through output policy map and if the sum of the bandwidth
percentages configured is below or above 100, the actual bandwidth is allocated proportionally. If the
sum of allocated bandwidth is less than 100, the unused bandwidth is allotted to un-allocated queues. If
the sums of allocated bandwidth exceed 100, then 1% of the bandwidth is derived for unassigned queues
from assigned queues.
• Allocate bandwidth to queues.
QOS-POLICY-OUT mode
bandwidth-percentage
Configure a Scheduler to Queue
By default, the MXL switch schedules packets for egress based on weighted round robin (WRR).
NOTE: The bandwidth and scheduler cannot be configured at the same time. Policy-level scheduler
assigned to queue is applied to both unicast and multicast traffic.
Setting DSCP Values for Egress Packets Based on Flow
Match-any Layer 3 flows may have several match criteria. All flows that match at least one of the match
criteria are mapped to the same queue because they are in the same class map.
Setting a DSCP value from QOS-POLICY-IN mode (refer to Setting a DSCP Value for Egress Packets)
assigns the same DSCP value to all of the matching flows in the class-map.
The flow-based DSCP marking feature allows you to assign different DSCP to each match criteria.
• Create matching flows within a class map that have different DSCP values.
CLASS MAP mode
match ip dscp 0–63 set-ip-dscp 0–63
The values you set from CLASS-MAP mode override the value you set in the QoS input policy DSCP
value. Packets matching the rule are marked with the specified value.
Example of Marking Flows in the Same Queue with Different DSCP Values
Dell#show run class-map
!
class-map match-any example-flowbased-dscp
match ip access-group test set-ip-dscp 2
match ip access-group test1 set-ip-dscp 4
match ip precedence 7 set-ip-dscp 1
Dell#show run qos-policy-input
!
qos-policy-input flowbased
set ip-dscp 3
738 Quality of Service (QoS)